The invention relates to a linear ball bush comprising a cage with a cage axis and having a plurality of ball circuits.
More particularly, this invention relates to a linear ball bush comprising a cage with a cage axis and having a plurality of ball circuits where each ball circuit comprises two straight ball rows substantially parallel to the cage axis, namely a carrier ball row and a return ball row, and two curved ball rows connecting the two straight ball rows. Each of the ball circuits rests radially outwardly on a runner plate which is inserted into a pertinent aperture of the cage and possesses an external surface to abut on an internal circumferential face of a bearing housing bore accommodating the cage. A closed track for the ball circuit in each case is formed on an inner surface of the runner plate. The closed track comprises two straight track sections, namely a carrier straight track section for the carrier ball row and a returning straight track section for the returning ball row, and two curved track sections connecting the straight track sections.
In relation to the outer face of the runner plate, the carrier straight track section lies at a higher level, in relation to the outer surface of the runner plate, the returning straight track section lies at a lower level, and the curved track sections gradually overcome the corresponding differences of level. The straight track sections are separated from one another by a middle rib. The carrier ball row in each case partially radially inwardly penetrates a slot of the cage, in order to be able to abut on a shaft enclosed by the cage, and the return ball row in each case is radially inwardly supported by the cage.
DE-AS-1,287,382 discloses a linear ball bush having an embodiment wherein the runner plate is formed as an annular shell with the straight track sections converging in extension upon a shell edging. In this embodiment, a prerequisite provided from the basic geometry is for steady ball guidance extending over the whole ball course, which could guarantee an impact-free running of the balls. On the other hand, the machining of the straight track sections--especially the carrying straight track section which requires careful machining--is made more difficult by the fact that the straight track sections meet with the shell edge with their imaginary prolongations.
DE-OS 2,003,535 discloses a runner plate which comprises only the carrying straight track section adjoined by partial arcs of curved track sections. The runner plate possesses no returning straight track section intersecting with the pertinent partial arcs of the curved track sections and accordingly no distinct rib to continue the carrying straight track section as far as the ends of the runner plate. Thus, the complete guidance of the balls on the track plate is not achieved over the entire ball circuit.
DE-OS 3,512,013 discloses a runner plate for linear ball bushes wherein the inner surfaces of the two straight track sections are separated from one another by a middle rib. The middle rib ends at respective distances from the ends of the runner plate. In each case, faces are formed between the end of the middle rib and the pertinent end of the runner plate plane which are parallel to the plane defined by the ball center points of the ball circuit. Thus, all lateral guidance of the balls in the region of the curved track sections is excluded. According to the disclosure of DE-OS 3,512,013, the necessity of a precise mutual adaptation of lateral guidance in the cage and lateral guidance in the runner plate is avoided in the region of the curved track section in each case.
It is an object of this invention to provide a linear ball bush having a configuration of its runner plate which, while maintaining the most complete possible ball guidance over the entire ball circuit, facilitates the machining of its straight track sections and especially of its carrying straight track section.